An ionic vinylene-linked three-dimensional covalent organic framework for selective and efficient trapping of ReO4− or 99TcO4−

The synthesis of ionic olefin linked three-dimensional covalent organic frameworks (3D COFs) is greatly challenging given the hardness of the formation of stable carbon-carbon double bonds (–C = C–). Herein, we report a general strategy for designing porous positively charged sp2 carbon-linked 3D COFs through the Aldol condensation promoted by quaternization. The obtained 3D COFs, namely TFPM-PZI and TAPM-PZI, showed impressive chemical stability. Furthermore, the positively charged frameworks with regular porosity endow 3D ionic COFs with selective capture radioactive ReO4−/TcO4− and great removal efficiency in simulated Hanford waste. This research not only broadens the category of 3D COFs but also promotes the application of COFs as efficient functional materials.


Supporting Experimental Procedures Section
Instruments. Fourier-transform infrared (FT-IR) spectra were recorded on a Nicolet Impact 410 FT-IR spectrometer. Powder X-ray diffraction (PXRD) data of the nanomaterials were collected on a Bruker AXS D8 Advance A25 Powder X-ray diffractometer (40 kV, 40 mA) using Cu Kα (λ=1.5406 Å) radiation. The morphology of the material was imaged by a scanning electron microscope (SEM, JEM-2010, JEOL). X-ray photoelectron spectroscopy (XPS) spectra were performed on a Thermo VG Multilab 2000X with Al Kα irradiation. The radiation stabilities of COFs were investigated in a GAMMATOR M-38-2 (USA) irradiator with a 60 Co source (γ-ray).
The hydrophilic property of the COFs was observed on a contact angle measuring instrument (JY-82B Kruss DSA). Solid-state 13 C cross-polarization magic-angle spinning ( 13 C CP/MAS NMR) spectra were recorded with a 4-mm double-resonance MAS probe; a sample spinning rate of 10.0 kHz, a contact time of 2 ms (ramp 100), and a pulse delay of 3 s were applied. The nitrogen adsorption and desorption isotherms were measured at 77 K using a Micromeritics ASAP 2020M system. The samples were outgassed at 120 °C for 12 h before the measurements. Surface areas were calculated from the adsorption data using Brunauer-Emmett-Teller (BET) methods. The pore-size-distribution curves were obtained via the non-local density functional theory (NLDFT) method. The thermal properties of the nanomaterials were evaluated using a STA PT1600 Linseis thermogravimetric analysis (TGA) instrument over the temperature range of 30 to 800 °C under nitrogen atmosphere with a heating rate of 10 °C/min. Metal ions concentrations were determined using an iCAP Q inductively coupled plasma mass spectrometry (ICP-MS, Thermo Fisher Scientific, USA). The light-absorbing property of samples is measured by an UV−vis−NIR spectrophotometer (LAMBDA950). Transmission electron microscope (TEM) were performed on a JEOL JEM-F200 electron microscope with an accelerating voltage of 200 kV.Materials and chemicals. All reagents were obtained from commercial sources and used as received. The Re ICP standard solution (1000 mg/L in 2% nitric acid) was purchased from Henan Wanjia R&D Center Co., Ltd. tetrakis(4formylphenyl)methane (TFPM) and 1,2,5-trimethylpyrazin-1-ium iodide (PZI) were purchased from Jilin Chinese Academy of Sciences-Yanshen Technology Co., Ltd.
Sodium Perrhenate (NaReO 4 ) was purchased from Energy Chemical Technology (Shanghai) Co., Ltd. Anhydrous 1-methyl-2-pyrrolidinone, N, N-dimethylformamide (DMF), dichloromethane, and acetonitrile were purchased from Sinopharm Chemical Reagent Co., Ltd. Ultrapure water was prepared from the Millipore system (18.25 MΩ·cm). All reagents were used without further purification, and all the experiments were conducted at room temperature.
Stability test. TFPM-PZI wes exposed to the boiling water, γ-ray irradiation (200 kGy), NaOH (6.0 M), and HCl (6.0 M) for 48 h, respectively. The mixture was then filtered and washed with ultra-pure water till the supernatant became neutral and dried under vacuum at 60 °C. Then, the FT-IR spectra and PXRD patterns were obtained.
Sorption isotherm study. The adsorption isotherms study of TFPM-PZI was conducted by adding 5 mg of adsorbent into 10 mL aqueous solutions of varying the initial concentrations of ReO 4 − (ca. 50-670 mg L -1 ), then stirred overnight to achieve equilibrium. The suspension was separated with a 0.22 µm nylon membrane filter for ICP-MS analysis. The adsorption capacity was calculated based on equation (1).
is the initial concentration and equilibrium concentration of ReO 4 − , respectively. m (mg) is the mass of the adsorbent and V (L) is the volume of the solution.
The Langmuir isotherm is based on the assumption that the adsorbent can only be adsorbed in a single layer on the adsorbent. The linear fitting of the Langmuir isotherm model is expressed by equation (2). ( where q m (mg g -1 ) is the maximum sorption capacity, k L is a constant indirectly where C t is the concentration of ReO 4 − at time t.
Pseudo first-order model and pseudo-second-order model are usually used for the sorption kinetics data fitting. The formulas were expressed in equations (5) and (6), respectively.
( ) where q e and q t are the adsorption capacity at equilibrium and time t, k 1 (g mg −1 min −1 ) and k 2 (g mg −1 min −1 ) are the rate constants of pseudo-first-order and pseudo-secondorder, respectively. The pseudo-first-order linear plot can be obtained by plotting ln (q e -q t ) versus t, and the pseudo-second-order linear plot can be obtained by plotting t/q t against.
where E(complex), E(Z + ), and E(anion) indicate the total energies of each complex, Z + , and anions, respectively. All calculations were performed using the Gaussian 09 program 69. to yield an orange solid.

Supporting Results and Discussion Section
Supplementary  TAPM-PZI calculated based on the 8-fold interpenetrated dia net.  .